1. Field of the Invention
The present invention relates to a tip seal for sealing used in a scroll member of a scroll type compressor and a manufacturing method of the tip seal.
2. Description of the Related Art
As shown in FIG. 5, a scroll type compressor is arranged such that a fixed scroll member A.sub.0 and a movable scroll member A.sub.1 are paired and disposed by being engaged to each other in a state that a standing wall B having an involute curve is disposed on the base of the scroll member A.sub.1 and the space between the standing walls B is used as a compression groove (compression chamber) D. Thus, a fluid is compressed in the compression chamber D, which is surrounded by both scroll walls, by eccentrically revolving the movable scroll member A.sub.1. In the scroll type compressor, a mounting groove C is formed along the top of the standing wall B and a long scroll-shaped tip seal 60 for sealing is fitted in the mounting groove C, as shown in JP-A-50-32512, JP-A-55-81296 and the like. The tip seal 60 is in compression contact with each of the confronting scroll members A.sub.0 and A.sub.1, that is, the tip seal 60 is in sliding compression contact with the top and bottom surfaces of the compression groove D defined by the scroll members A.sub.0 and A.sub.1 and is in compression sealing contact with the mounting groove C so that the compression chamber can be hermetically sealed to maintain the airtightness thereof.
Since the tip seal serves as a sealing-device by being fitted in the mounting groove C, it has a slender scroll shape and is made by injection molding. A conventional method of manufacturing the tip seal is disclosed in JP-A-4-262087, in which a synthetic resin is supplied up to both ends of a mold for a scroll-shaped tip seal by providing a side gate, through which the synthetic resin is to be injected, on a side of the mold for the tip seal at the substantially intermediate portion of the entire length thereof.
When the manufacturing method in which the gate is provided on the side of the mold for the tip seal at a substantially intermediate portion of the entire length thereof is employed, a convex portion m is formed as a gate trace on a side of a tip seal 60 as a molded product as shown in FIG. 6, by which an intimate contact property between the tip seal 60 and the side of the mounting groove C is prevented, so that a sealing property is lowered. To solve this problem, the tip seal is made by injection molding with a side gate provided at a portion which is an outside end of a mold for a scroll-shaped tip seal in a method disclosed in JP-A-6-137285, so that a sealing property of the tip seal is improved by preventing the formation of a gate trace on a side of the tip seal.
In the method disclosed in JP-A-6-137285, however, since the side gate is provided at the portion of the mold corresponding to the outside end of a scroll-shaped tip seal when manufacturing the tip seal by injection molding, the tip seal is molded integrally with a runner through the gate. Thus, not only a process for cutting off the runner is needed but also a convex portion n of 1-2 mm is formed on the outside end of the tip seal as a gate trace when the runner is cut off as shown in FIG. 1 (FIG. 7 of the present application) of the published application of the prior art. To fit the tip seal in which the convex portion n is formed in the mounting groove C as it is, the tip seal 60 must be shortened by the size of the convex portion n, thus a sealing property at the portion is lowered and a compressing performance of a compressor cannot be increased. Further, when the gate is provided on the end of the center side (on a high pressure side) of the mold for the tip seal, whereby the compression performance is greatly lowered, thus the gate must be disposed on the outer end of the mold. Further, when executing the process of removing the convex portion n, since the tip seal 60 has a slender shape and elasticity as a whole and has an involute curve, it is difficult to set the tip seal 60 at a predetermined position and thus the process for removing it leads to a great expense.
Here, and in the following claims the term "submarine gate" is defined as follows; It is a kind of tunnel gate provided in a mold wall for injection molding and transfer molding. Molten resin from a runner of the mold passes below the parting line thereof and is injected through the submarine gate into a cavity of the mold from the position right above an edge of the cavity of the mold.
An object of the present invention is to easily manufacture a tip seal excellent in a sealing property without a convex portion caused by a gate trace by providing a submarine gate at the portion of the molding cavity of a mold for molding the end of a tip seal main body and injecting a synthetic resin through the submarine gate.